Interverterbal disc space shavers are frequently utilized to prepare the intervertebral disc for interbody fusion cages. However, it is often the case that too much cortical bone is removed when decorticating the vertebral endplates. As a result, the vertebrae are undesirably weakened. Shavers are one of the many sources believed to create endplate damage due to the aggressive force during shaving, improper shaver size, access/insertion trajectory angle and/or endplate irregularities, and shape that is not congruent to the disc space.
US Patent Publication no. 2007-0233130 (Suddaby) discloses tool for preparing vertebral surfaces following a discectomy has a body and a rotary cutting tool mounted at the distal end of a lever which extends through the body. The proximal end of the lever can be squeezed toward the body to force the cutting tool against the vertebral surface facing it, while the tool is rotated by turning a crank supported on the tool body, or by a motor. The cutting tool is preferably a flexible rasp or blade which can conform to and control the convexity of the prepared surface.
U.S. Pat. No. 5,454,827 (Re. 38,335) (Aust) discloses a surgical instrument includes a handle, a first stem section having a longitudinal axis and extending from the handle, and a tissue engaging member for engaging tissue. A second stem section, connected between the first stem section and the tissue engaging member, has a portion which is bendable and supports the tissue engaging member for movement between a plurality of orientations relative to the axis and to the first stem section. The surgical instrument includes a system for bending the bendable portion of the second stem section to change the orientation of the tissue engaging member relative to the axis and to the first stem section from a first orientation to a second orientation. The bendable portion of the second stem section includes a member for enabling bending movement of the bendable portion to locate the tissue engaging member at the same angle relative to the longitudinal axis of the first stem section at more than one location along the length of the bendable portion. The marketed version of this flexible shaver claims to minimize endplate damage.
US Patent Publication Numbers 2008-0221586 and 2010-0076502 (Alphatec I and II) disclose a curvilinear access device having an expandable working portal. 2010-0076502 discloses a curved cannula (FIG. 22) having a distally extending tooth (FIG. 42); a curved stylet (FIGS. 26 and 77); a curved guidewire (FIG. 78) in a telescoping cannula (FIG. 59b); and a jointed endplate shaver (FIGS. 67a and 95).